In DE 33 14 770 C2, a device for the operation of a motor-driven windshield wiper system was introduced. This system uses a beam director mounted directly on the inner surface of the windshield. The beam director is associated with a beam transmitter which emits rays through the windshield. If there is the least reflection at the exterior surface of the windshield because of moisture which is present, some portion of the rays are directed to an associated beam receptor.
The attachment of such beam directors to a windshield may be achieved by means of optical adhesives. However, this presents two problems: certifying perfect adhesion and guaranteeing perfect beam paths. Every variation in alignment of the beam directors and discontinuities in the beam paths potentially interferes with the device's reading, and therefore may affect the operation of the windshield wiper system.
Therefore, the needs have arisen for a moisture sensor device which guarantees that (1) the inner windshield surface and the beam director surfaces are parallel, and (2) the optical adhesive is applied uniformly between the windshield and the beam director.